Modified Project Summary/Abstract Section Attention deficit/hyperactivity disorder (ADHD) is a prevalent neuropsychiatric illness affecting 5 to 9% of children and 1 to 5% of adults. Oral administration of psychostimulant medication such as amphetamine (e.g., Adderall) is a first-line treatment to combat ADHD-associated deficits. A priority at the National Institute of Mental Health is to examine and improve upon existing therapeutic strategies for illnesses such as ADHD. Although short-term therapeutic effects of amphetamine have been established, less is known concerning the long-term effects of chronic administration. Assessment of repeated therapeutic amphetamine use has become especially critical because childhood ADHD is now known to often persist into adolescence and adulthood, increasing the potential for protracted amphetamine use. The overall goal of the current project is to assess behavioral and neurochemical effects of oral therapeutic doses of chronic d-amphetamine. An accepted behavioral model for testing agents that are effective in treating ADHD (a serial reaction-time task) will be used to determine a therapeutic dose of oral d-amphetamine. Once therapeutic doses are determined, they will be administered under a chronic regimen to assess long-term behavioral and neurochemical effects. Findings from the current studies will provide important new data on chronic therapeutic amphetamine treatment.